System and method of surfactant dosing

ABSTRACT

A system and method of processing laundry by the determination of surface tension in a dynamic environment for surfactant concentration in industrial laundry applications. The dosage system is able to control the surfactant concentration for a recycle wash tank and preferentially the washer tank using surface tension measurements, temperature control, and correlation to the percentage of active matter based on a full dose of a commercial surfactant for the wash runs. The dosage system preferably uses a surface tensiometer able to monitor surfactant levels and to constantly dose surfactant for use in subsequent washes.

FIELD OF THE INVENTION

[0001] The present invention relates to a process for central processingof home laundry that improves efficiency and reduces environmentalimpact by recycling water and chemicals.

BACKGROUND OF THE INVENTION

[0002] The United States is increasingly burdened with higher potablewater demands and more costly downstream water treatment processes. As apractical matter, the costs for water treatment and supply areultimately borne by the consumer. Reductions in these costs, whereeconomically feasible, draw strong political and commercial support.

[0003] Military, industrial, and residential sources generate voluminousquantities of “gray water” from dishwashers, wash vessels, sinks,showers, and bathtubs. These devices generate gray water and typicallylack any form of recycling system. A large number of states have adoptedcodes for reuse of gray water. Therefore, the impetus for developingrobust and economical separation strategies is a reality. The Departmentof Energy (“DoE”) is pushing the private sector to develop moreefficient, lower-water usage washing machines with minimal byproductsthat are capable of using cold water.

[0004] There exists a need to reuse water in a system for washingconsumer laundry outside of the home. Reuse of the water used in laundryapplications would recycle surfactant to the washing machines. As aresult, there exists a need to develop a method to monitor surfactantcontent in the recycled water to allow appropriate dosing of detergentto the washing machines.

SUMMARY OF THE INVENTION

[0005] The present invention provides a system and method of processinglaundry by the determination of surface tension in a dynamic environmentfor surfactant concentration in industrial laundry applications. Usingthe system and method, an operator is able to reduce surfactant cost inhis process by delivering the correct dosage for subsequent washes viathe continual adjustment of detergent concentration in the recycle washtank. The dosage system is able to control the surfactant concentrationfor a recycle wash tank using surface tension measurements, temperaturecontrol, and correlation to the percentage of active matter based on afull dose of a commercial surfactant for the wash runs. In a preferredembodiment, the dosage system, using a surface tensiometer able toconstantly monitor surfactant values in reference to a target surfacetension set point, sends an output to an external pump to constantlydose a recycle tank. The adjusted surfactant dosage in the wash tank isthen available for use for subsequent washes.

[0006] The determination of surface tension in a dynamic environmentholds many possibilities as a control mechanism for surfactantconcentration in industrial laundry applications. In a commerciallaundry process, a surfactant dosage system is needed to maintain theeconomic advantage of delivering a correct dosage of surfactant tosubsequent wash runs of a recycle wash operation. It is preferable toaccomplish this without the verification of the surfactant concentrationusing standard wet chemistry analytical methods that would be tooexpensive for a commercial operation. Using the system and methoddescribed herein, an operator is able to reduce surfactant cost in hisprocess by delivering the correct dosage for subsequent washes via thecontinual adjustment of detergent concentration in the recycle washtank.

[0007] The present invention includes a surfactant dosing system usingthe nonequilibrium continuous monitoring of surface tension valuescorrelated to surfactant concentration based on the percentage of activematter in an industrial laundry process. In one embodiment, standardlaboratory methods are used to correlate surface tension measurements toactive matter determination at selected temperatures for a commercialdetergent. This method allows for the determination of a curve forpredicting percentage active matter based on nonequilibrium surfacetension measurements for selected samples at defined temperatures. Thedetermining of the surface tension for a full dose of detergent andcorrelating this value to a percentage of active matter at a standardtemperature allows for the operator to determine a baseline for propermonitoring of surfactant concentration in an industrial process.

[0008] The dosage system is able to control the surfactant concentrationfor a recycle wash tank using surface tension measurements, temperaturecontrol, and correlation to the percentage of active matter based on afull dose of a commercial surfactant for the wash runs. Specifically,the dosage system using the surface tensiometer is able to constantlymonitor surfactant values and basis a target surface tension set point,send an output to an external pump to constantly dose a recycle tank.The adjusted surfactant dosage in the wash tank is then available foruse for subsequent washes.

[0009] In another embodiment, the system and method is capable ofanalyzing a wash recycle collection tank and determining a surfacetension at any instant. After developing a correlation curve of activematter to surface tension, the present invention may read the surfacetension value and adjust surfactant concentration using electronicalgorithms. Using these algorithms to determine the delivery dosage ofdetergent scaled to a specific concentration, the liquid detergent ismetered to provide a percentage of stroke length of the dispenser, thusproviding an adjusted dose to individual washers from a wash recycletank.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A more particular description of the invention, brieflysummarized above, may be had by reference to the embodiments thereof,which are illustrated in the appended drawings and described herein. Itis to be noted, however, that the appended drawings illustrate only someembodiments of the invention and are therefore not to be consideredlimiting of its scope, because the invention may admit to other equallyeffective embodiments.

[0011]FIG. 1 is a preferred embodiment of the surfactant dosage system;

[0012]FIG. 2 is another embodiment of the surfactant dosage system;

[0013]FIG. 3 is another embodiment of the surfactant dosage system;

[0014]FIG. 4A is a partial embodiment of the surface tension module;

[0015]FIG. 4B is a partial embodiment of the surface tension module;

[0016]FIG. 5 is a graph comparing surface tension with detergentconcentrations and bubble rates related to TABLE 2; and

[0017]FIG. 6 is a graph comparing surface tension with detergentconcentrations and bubble rates related to TABLE 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] Though those skilled in the art will recognize that the teachingsand scope of this invention are not limited to the following, thisdisclosure provides some of the preferred embodiments of the invention.

[0019] Surface tension varies as active surfactants are used.Surfactants are used because of their ability to reduce surface tensionin water-based and solvent-based formulations. Dynamic surface tension,rather than equilibrium surface tension, can be measured in turbulentenvironments such as laundry processing since it may require severalminutes for surfactant molecules to diffuse to the interface and lowerthe surface tension to an equilibrium level. Dynamic surface tensiondirectly impacts the quality of spreading and adhesion. Surfactants usedin fluid formulations tend to be quite surface active, and can varysignificantly with respect to diffusion rate, depending on molecularweight and structure.

[0020] The system shown in FIG. 1 shows an application of using atensiometer 10 in a laundry processing application. Using an automaticsurface tensiometer 10, such as an IP6000 manufactured by 2000 SensaDyneInstrument Division, the user can then program a set point to send asignal to a commercial pump and dose a collection tank, therebyconstantly monitoring the surfactant concentration for subsequent washruns. Any tensiometer, including in-process, on-line tensiometers, maybe used with the present invention. In a preferred embodiment, thetensiometer may have the capability to control formulation additive andconcentration levels using integrated analog outputs for surface tensionand temperature. Moreover, the tensiometer may include high and low setpoint alarms that may be used for a variety of applications such assurface tension and temperature.

[0021] During subsequent washes the wash water is released from thewasher 16 to a dump chest 18 and processed through a lint screen or linttrap 20 and separatory filter 22. The measuring probes 24 attached to asampling chamber 26 on the recycle wash tank 28 constantly monitor thesurface tension and temperature. As the filtered water enters therecycle wash tank 28 via a pump, the surface tension monitors the valueand compares it to the set point. If the surface tension value readsabove the set point, the tensiometer 10 sends a signal that is capturedby the black box converter 30 and configured into an acceptable signalfor a dispenser 32 such as the Knight dispenser shown in FIG. 1.

[0022] Surface tension measurements generated using a Dynamic Surfacetensiometer are preferably taken in a non-turbulent (quiet) zone inorder to reduce variations in fluid flow across the sampling chamberduring measurement. As bubbles are generated in the process, it isdesirable to maintain a consistent less turbulent flow through thesampling chamber, so that the bubbles are completely formed andinterpreted correctly by the system. In a preferred embodiment, it ispossible to achieve this quiet zone by taking a slip stream (preferablyabout 100 ml/min) from the bulk of the recycled water being pumpedaround the recycle wash tank to provide a pressurized supply to refillthe washing machine. This slipstream may be routed into the bottom ofsampling chamber 26, which in turn could overflow back into the recyclewash tank. This procedure not only provides a most preferable quiet zonebut also provides a constant water level in the sample chamber.

[0023] When the dispenser 32 receives the signal to begin pumping, thedispenser 32 turns on for a selected amount of time. Those skilled inthe art recognize that the duration may vary widely or even be unlimitedin the case of continuous dosing. In a preferred embodiment, a typicalrange of times for dosing may be from about one to about five seconds induration with a typical evaluation time of about fifteen to about thirtyseconds before redosing the tank. These times are only an example of oneembodiment and are expected to vary widely depending on numerousvariables.

[0024] During the design of the process the operator has two dosingoptions. The operator may elect to dose directly into the washer 16 orto dose directly into the recycle wash tank 28. The latter option maynegate the effect of temperature variations on nonequilibrium surfacetension in the recycle wash tank 28.

[0025] The tank 28 should be kept at a semi-constant temperature duringoperation by the constant exchange of filtered water at temperature.However, the delivery mechanism can easily be set up ahead of time toaccommodate delivery to the washer 16 also. It is preferable that onlyone delivery option may be used at any one time.

[0026] In a preferred process, a dose of surfactant is sent to therecycle wash tank 28 that is then evaluated against the set point andthe monitoring and dosing process begins again until the set point isreached. The evaluation time is determined from preliminary work and isthe amount of time between surface tension readings and comparisons tothe set point.

[0027] Referring to FIG. 2, a preferred embodiment of the surfactantdosing system, a controller interfaces with the surface tensiometer 10.The controller monitors surfactant level within a tank 28. Thecontroller is preferably capable of activating a pump at a desiredsurface tension and issuing a surfactant dose relevant to time. The taskis preferably accomplished by using a Versamax Micro Programmable LogicController along with a signal-conditioning transmitter.

[0028] Though those skilled in the art will recognize that while manymethods may be used to accomplish this task, two methods are preferable.First, the tensiometer 10 preferably provides a 0 to 10-volt output thatcan be used as an input to a signal conditioner. The conditioner ispreferably capable of converting this input to a 4 to 20-ma signal thatwas sent to the programmable logic controller. Ladder logic may be usedto compare the signal to a constant. In the event that the signal wasgreater than or equal to the constant, a pump may activate for a desiredtime and disperse surfactant. It is advantageous to include a pause timein the logic between dispersions to allow adequate mixing.

[0029] Alternatively, using preferred digital outputs from thetensiometer 10 enables the operator to select a desired surface tensionusing the keypad of the tensiometer 10. Once the desired surface tensionis reached, the output can activate an input to the programmable logiccontroller, which would begin the logic sequence as previouslydiscussed.

[0030] The present invention allows for correlating the percentage ofactive matter for a standard detergent use concentration with surfacetension at standard temperatures in an industrial cleaning process.Using this data and determining the surface tension and the percentageof active matter determination for a full dose of detergent, a curve canbe constructed using surface tension measurements correlated to activematter analyses for selected sample points in the process.

[0031] In the development of this process, this was accomplished using ahand held surface tensiometer, manufactured by SITA Messtechnik GmbH ina preferred embodiment, set at a standard bubble rate to measure thesurface tension at a set bubble rate and desired temperature for thecollected samples. The procedure may be automated using a tensiometersuch as the Sensadyne model IP6000 tensiometer set to a standard bubblerate. This allows the user to program a tensiometer set point that canbe used to activate a pump to deliver surfactant when the surfacetension is too high.

[0032] Referring to FIG. 3, a larger scale embodiment of the presentinvention is shown. Those skilled in the art will recognize the pipingshown in FIG. 3 is but one arrangement of the elements of the inventionand substitution, rearrangement, addition, and/or deletion of elements,including pipes, valves, drain, controllers, and any other elementdepicted herein, are considered to be within the scope of the invention.Streams 100-112 interact with the system. The figure is presented in aclockwise fashion showing how the soft water 100, dirty rinse water 102,dirty wash water 104, liquid detergent 106, recycle rinse water 108,return loop 110, and recycle wash water 112 interact with the system.

[0033] As shown a rinse water sump pump 118 is connected to a rinsewater sump 120 that in turn is connected to the rinse water lint screen122. Dirty rinse water moves into the rinse water sump 120. The rinsewater lint screen is connected to the rinse feed tank 124 whilediverting lint and other foreign particles to the wet unit to dumpster126.

[0034] From the rinse feed tank 124, a rinse feed pump 128 can directflow back to the rinse feed tank 124 or via a rinse circulation pump 130to the rinse filter 132. The rinse filter is connected, amongst otherthings, the recycle rinse water tank 134.

[0035] The recycle rinse water tank 134 is connected to the recyclerinse water tank pump 136 which is capable of moving recycle rinse water108 fluid to, amongst other locations, the rinse water ultraviolet(“UV”) unit 138. Nearby, a back flush pump 140 is connected at a valveprior to the rinse water pump 136 that allows for the movement of liquidto the rinse feed pump 128/rinse circulation pump 130 and the washcirculation pump 154/wash feed pump 156.

[0036] As shown, the wash water heater 142 is connected to the washwater UV unit 144 such that the recycle wash water pump 146 can moverecycle wash water 112 to the wash water heater 142. The wash waterheater 142 is connected to the recycle wash water tank 148. Soft water100 enters the system into the recycle rinse water tank 134 and therecycle wash water tank 148.

[0037] The liquid detergent metering pump 150 can also move liquiddetergent 106 into the recycle wash water tank 148. With these elementsdescribed and shown in FIG. 3, the use of a surface tension module 200as shown in communication with the recycle wash water pump 148 allowsfor the surface tension module 200 to activate the liquid detergentmetering pump 150 consistent with the teachings of this invention. Therecycle wash water tank is also connected to the wash filter 152 whichis capable of filtering wash water from the wash feed tank 158 via thewash circulation pump 154 and the wash feed pump 156 and from returnloop 110.

[0038] As arranged in the rinse portion of FIG. 3, a wash water lintscreen 160 is connected to the wash feed tank 158 which accepts liquidfrom the wash water sump pump 162 and is capable of diverting lint andother particulates to the wet unit to dumpster 126.

[0039] A wash water sump 164 collects dirty wash water 104 and in turnallows the wash water sump pump 162 to move the dirty wash water to thewash water lint screen 160. The clean-in-place tank 166 receives feedfrom both the rinse circulation pump 130 and the wash feed tank 158.

[0040] An electrical layout of the surface tension module 200 is shownin FIGS. 4A and 4B. The front 202 of the surface tension module 200 maycontain indicators such as the Start indicator 204 and the Stopindicator 206 shown herein. These indicators are connected to theprogrammable logic controller 208. As shown herein, the programmablelogic controller 208 uses a 24-volt DC power supply. The programmablelogic controller 208 is connected to a signal conditioner 212 that is inturn connected to a sensor 214 such as the SensaDyne sensors describedherein. The programmable logic controller 208 is finally connected tothe liquid detergent pump 150 as previously discussed for use in theinvention.

[0041] Though those skilled in the art will recognize that the benefitsof present invention may be enabled in various embodiments, oneembodiment allows for analyzing a wash recycle collection tank anddetermining a surface tension at any instant. Through previous work withthe development of a correlation curve of active matter to surfacetension, it is possible to read this surface tension value and adjustsurfactant concentration using electronic algorithms. The detergent inthe wash recycle tank is evaluated and compared to a full dose ofdetergent. The algorithms determine the delivery dosage of detergentscaled to a specific concentration and metered by stroke length on adelivery pump. The programmable logic controller then sends a signal topump for a specific time as a percentage of stroke length equal to afull dose. Further, through the use of this method, it is possible toadjust a full dose of detergent and deliver this adjusted dose toindividual washers from a wash recycle tank. This method offers moreflexibility in that only the make-up dosage of surfactant is deliveredto an individual washer rather than a full dose as previously describedherein. It is possible that more equipment and electronics may be neededto perform this embodiment.

EXAMPLES

[0042] Through a continual monitoring of surface tension the user candesign a system to maintain a wash water supply tank at a constantsurfactant level for subsequent washes. Using a Sensadyne laboratorytensiometer, the surface tensions of different concentrations of astandard laundry detergent were tested at different bubble rates. Thepercentage mass flow concentration compared to the bubble ratesexpressed bubbles/second were: TABLE 1 Mass Flow ConcentrationComparison to Bubbles Per Second Mass Flow Concentration Bubbles/second 7% 1  9% 2 25% 5 60% 10 99% 15

[0043] Expected results were that higher nonequilibrium surface tensionswould be obtained at higher bubble rates due to less time beingavailable for surfactant to diffuse to the interface to reduce thesurface tension. The desired outcome was to use this dynamic surfacetension measured at an optimum bubble rate in a one-to-one correlationwith detergent concentration in the concentration range of interest.

[0044] The results were consistent and expected in that dynamic surfacetension decreased with increasing detergent concentration and decreasingbubble rate, i.e., increasing bubble age. However, at a given bubblerate, a one-to-one correlation of surface tension and detergentconcentration was obtained.

[0045] The results were plotted and produced curves that may serve as acalibration curve to monitor changes in surfactant concentration overtime in the laundry process. Additionally, Liquid Tide® HE samples weresent and tested independently at the Sensadyne laboratories. Resultsfrom the SensaDyne testing produced more extensive results.

[0046] Liquid Tide® HE was chosen as the test surfactant. This detergentcontains 22.8% alcohol ethoxysulphate based on Neodol 25-2, 4.2% cocosoap and 4% alcohol ethoxylate. The rest of the product is primarilywater and propylene glycol with a few other minor non-surfactantingredients. Standard use concentration is 4.36 g/L.

[0047] In the studies, surface tension readings were measured at 1, 3,5, and 8 bubbles/second at detergent concentrations at and below thestandard use concentration. Deionized water was used as the solvent, andmeasurements were performed at room temperature.

[0048] The procedure involved calibrating the tensiometer to a specificbubble rate, evaluating the different test concentrations at the setbubble rate, changing the bubble rate, re-calibrating the instrument,and measuring the test concentrations at this new bubble rate. In orderto produce a curve this procedure was repeated for 1, 3, 5, and 8bubbles/second. Additionally, a sample of Liquid Tide® detergent wastested at various concentrations and bubble rates over time.

[0049] From these tests, the following data was developed: TABLE 2Determination of Surfactant Concentration Using Dynamic Surface TensionSurfactant concentration Bubbles/second % 1 3 5 8 0.436 39.2 46.2 47.547.4 0.336 40.6 48.2 49.6 51.2 0.236 43.3 52.3 53.6 55.6

[0050] These results have been plotted in FIG. 5, showing therelationship of surfactant concentration, surface tension, and bubblerate.

[0051] A neat solution of Liquid Tide® detergent was diluted to aspecific concentration to explore surface tension as the bubble ratechanges over time. The procedure involved using the Dynamic SurfaceTensiometer with an automatic dispensing unit. Using a mass flowcontroller on the instrument set a specific bubble rate. The mass flowcontroller was set to a calibrated percentage equal to a pre-determinedbubble/second measurement. The dispenser unit used could only be set upin equal incremental percentages. Therefore, a concentration range from0.05% concentration to 0.5% concentration, in 11 incremental steps of0.05% concentration each, was chosen. The bubble/second range wasevaluated at 1, 2, 5, 10, and 15 bubbles/second.

[0052] Similarly, the following results were obtained using Liquid Tide®detergent as a surfactant: TABLE 3 Determination of SurfactantConcentration Using Dynamic Surface Tension Surfactant Bubbles/secondconcentration % 1 2 5 10 15 0.05 72.75 72.88 72.78 72.81 72.69 0.1 54.7362.38 69.25 70.29 67.97 0.15 50.18 57.16 64.77 68.79 67.24 0.2 46.6552.48 60.75 67.53 67 0.25 44.16 49.62 58.37 66.65 66.6 0.3 42.51 47.8155.53 64.81 65.61 0.35 41.52 46.44 54.23 62.89 65.47 0.4 39.6 45.4 52.2961.02 65.12 0.45 38.75 44.85 51.19 59.59 64.22 0.5 38.34 44.11 50.0458.41 63.7 0.55 37.94 43.44 49.29 57.56 62.87

[0053] These results have been plotted in FIG. 6, showing therelationship of surfactant concentration, surface tension, and bubblerate.

[0054] A closed loop cleaning pilot plant was used to test theefficiency of the unit along with the quality of the finished products(consumer clothing). During this period, a target of 75% water recoverywas maintained for the entire system. This target was maintained bypurging 25% of the wash cycle water, remaking the wash water volume withrinse water and then remaking the rinse water volume with fresh softenedwater. Surfactant recovery during this period was 24%.

[0055] Previous testing and calculations had determined a full dose ofTide® detergent for 10 pounds of soiled material would be 70 grams intoabout 10 gallons of water. During the test period stated, 91 loads ofwash were processed using an average of 53 grams Tide® detergent addedper load. This yields a surfactant recovery of 24% for the period.

[0056] Numerous aspects of the invention may be varied without departingfrom the scope of the invention. The parameters may be varied, dependingon the situation and the specific parameters desired. With regard toeach parameter, a preferred parameter or range has been shown, but thoseskilled in the art should recognize that these parameters are notdefinitive, but illustrative of the benefits of a preferred embodimentof the invention.

We claim:
 1. A system of surfactant dosing for maintaining a set pointof surfactant level in a laundry application comprising: a washer tank;a recycle wash tank connected to the washer tank; a dispenser; and atensiometer wherein: the tensiometer is capable of measuring thesurfactant level in the recycle wash tank; the tensiometer is capable ofcomparing the surfactant level to the set point; and the tensiometer iscapable of sending signals to the dispenser.
 2. The system of claim 1wherein the dispenser is capable of pumping surfactant to the recyclewash tank.
 3. The system of claim 1 wherein the dispenser is capable ofpumping surfactant to the washer tank.
 4. The system of claim 1 furthercomprising a converter disposed between the tensiometer and thedispenser capable of configuring and forwarding signals to thedispenser.
 5. The system of claim 1 further comprising a controllerdisposed between the tensiometer and the dispenser wherein: thecontroller is capable of monitoring the surfactant level; and thecontroller is capable of activating the dispenser.
 6. The system ofclaim 5 wherein the controller comprises a programmable logic controllerand a signal-conditioning transmitter.
 7. The system of claim 6 whereinthe programmable logic controller is capable of using ladder logic tocompare the signals to a constant.
 8. The system of claim 1 furthercomprising a programmable logic controller and wherein the tensiometercomprises: a keypad; and at least one digital output; wherein thedigital output from the tensiometer is capable of activating theprogrammable logic controller.
 9. The system of claim 1 furthercomprising: a dump chest connected to the washer tank; a lint screen ora lint trap connected to the dump chest; and a separatory filterconnected the lint screen or lint trap and connected to the recycle washtank; wherein the recycle wash tank comprises a sampling chamber suchthat the tensiometer is capable measuring the surfactant level of therecycle wash tank via the sampling chamber.
 10. The system of claim 2wherein the dispenser is capable of dosing a calculated percentage of astroke length of the dispenser.
 11. A method of surfactant dosing formaintaining a set point of surfactant level in a laundry applicationthat comprises the steps of: (a) measuring the surfactant level by usinga tensiometer is capable measuring the surfactant level; (b) comparingthe surfactant level to the set point; (c) pumping surfactant if thesurfactant level is lower than that the set point.
 12. The method ofclaim 11 wherein Step (a) is accomplished by measuring the surfactantlevel in a recycle wash tank, wherein the recycle wash tank is connectedto a washer tank.
 13. The method of claim 12 wherein Step (c) isaccomplished by pumping surfactant into the recycle wash tank.
 14. Themethod of claim 12 wherein Step (c) is accomplished by pumpingsurfactant into the washer tank.
 15. The method of claim 11 wherein Step(b) further comprises the steps of: producing signals with thetensiometer; converter the signals from the tensiometer; and deliveringthe converted signals to a dispenser capable of performing Step (c). 16.The method of claim 11 which further comprises the step of using acontroller connected to the tensiometer to accomplish Step (b).
 17. Themethod of claim 16 wherein the controller comprises a programmable logiccontroller.
 18. The method of claim 17 which further comprises the stepof using ladder logic to compare the signals to a constant.
 19. Themethod of claim 11 which further comprises correlating a percentage ofactive matter to the measured surfactant level from Step (a).
 20. Themethod of claim 17 which further comprises the step of constructing acurve of the correlation of percentage of active matter to the measuredsurfactant level measurements.
 21. The method of claim 11 which furthercomprises the step of adjusting surface tension using electronicalgorithms to deliver an adjusted dosage.
 22. The method of claim 21which further comprises the steps of: developing a correlation curve ofactive matter to surface tension; and metering the dosage as apercentage of a stroke length.
 23. A system of surfactant dosing formaintaining a set point of surfactant level in a laundry applicationcomprising: a washer tank; a dump chest connected to the washer tank; alint screen or a lint trap connected to the dump chest; a separatoryfilter connected to the lint screen or lint trap; a recycle wash tankconnected to the separatory filter and connected to the washer tank; asampling chamber connected to the recycle wash tank; a tensiometerwherein the tensiometer comprises measuring probes disposed in thesampling chamber; and a dispenser capable of pumping surfactant to therecycle wash tank; wherein the tensiometer is capable measuring thesurfactant level and comparing the surfactant level to the set point;and wherein the tensiometer is capable of sending signals to thedispenser.
 24. The system of claim 23 further comprising a converterconnected to the tensiometer and the dispenser wherein the converter iscapable of converting signals from the tensiometer and sending theconverted signals to the dispenser.
 25. The system of claim 23 furthercomprising a programmable logic controller.